CVE-2026-88167 in Office
Summary
by MITRE • 10/14/2026
Buffer over-read in Microsoft Office Word allows an unauthorized attacker to disclose information over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described constitutes a buffer over-read flaw within the core processing engine of Microsoft Office Word, specifically affecting how the application handles certain document structures or embedded objects during parsing operations. This type of memory corruption issue arises when the software reads data from a memory location beyond the bounds of an allocated buffer without proper validation checks to ensure that the requested read operation does not exceed the available memory space. In the context of Microsoft Office Word, this often occurs when processing complex document elements such as embedded OLE objects, specific formatting codes, or malformed XML structures within .docx files. The root cause typically lies in insufficient boundary checking during the parsing phase, where an attacker can craft a malicious file that triggers the application to access memory addresses outside the intended buffer limits. This behavior is classified under CWE-126, which denotes Buffer Over-read, indicating that while the immediate consequence may not be direct code execution as seen with over-writes, it still represents a significant deviation from secure coding practices regarding memory management and data integrity verification.
The operational impact of this vulnerability centers on unauthorized information disclosure rather than remote code execution or denial of service in its most severe forms. When an attacker successfully exploits this buffer over-read condition by tricking a user into opening a specially crafted document, the application may inadvertently expose sensitive contents from adjacent memory regions to the network stack or local system logs depending on how the error is handled and propagated. This could include partial disclosure of heap metadata, pointers to other objects in memory, or potentially credentials if they reside in nearby allocated buffers. The attack vector typically involves social engineering tactics where a victim is persuaded to open an attachment from an untrusted source, aligning with ATT&CK technique T1566.001 (Spearphishing Attachment). Once the malicious document is processed locally, the vulnerability allows for potential data exfiltration if the application attempts to report the error or process subsequent commands based on corrupted state information that leaks memory contents back through network interfaces or logging mechanisms integrated into the Office suite.
Mitigation strategies must address both immediate remediation and long-term defensive posture improvements. The primary defense is the timely installation of security updates provided by Microsoft, which patch these parsing logic flaws by enforcing stricter bounds checking during document interpretation. Organizations should ensure that all endpoints running Microsoft Office are configured to receive automatic security patches or have a rigorous update management policy in place. Additionally, implementing application control policies such as AppLocker or Windows Defender Application Control can prevent the execution of untrusted scripts and macros often associated with delivering these malicious documents. Users must be educated on recognizing suspicious attachments and verifying sender authenticity before opening files. From an architectural perspective, enabling Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) provides layers of defense that make exploitation more difficult by randomizing memory layouts and preventing code execution in non-executable memory regions, thereby reducing the likelihood that a successful over-read can be leveraged for further malicious activities.